Research will be directed towards elucidation of the conformational consequences and biological significance of the interaction of both the histones and non-histone proteins, found in the nucleus, with DNA. The research program to be pursued involves the isolation, biochemical characterization immunological studies, and biophysical analysis of chromatin fragments containing varying numbers of nucleosomes from chicken erythrocytes. Careful control of ionic strength and composition, as well as protein content of the chromatin subunits, will permit a systematic study of the conformational features by various biophysical techniques, e.g., circular dichroism, nuclear magnetic resonance, polarization of fluorescence, etc. It is anticipated that the existence and structural parameters of the higher levels of DNA organization can be elucidated by employing small oligonucleosomes capable of attaining stable compact structures corresponding to discrete levels of DNA orgainzation. Detailed studies will be carried out on chromatin to study the effect of acetylation of H3 and H4 on the conformation and stability of both monomers and high molecular weight material. The effect on condensation of phosphorylated Hl will be also studied. Determination of the structural characteristics required for complete condensation of DNA, thus rendering it less accessible to enzymes, may aid understanding of the process of decondensation and gene activation.